Believe it or not, Rocky Balboa, the character Sylvester Stallone made famous across six movies about the boxer, was very nearly a member of G.I. Joe. It was early 1986 and Hasbro was very close to finalizing a deal to add the character to a future wave of figures. Rocky IV had come out in 1985 and it featured Rocky defeating Ivan Drago and basically winning the Cold War against he Soviets by doing so. How close was the deal to happening? Well, they made the card art for the figure, for one thing:
And they even had him appear in the G.I. Joe comic book by Marvel. They had a 4-issue series listing every character, called G.I. Joe: The Order of Battle. In issue #2, you can see this:
But the deal fell apart. Stallone decided to grant his likeness rights instead to a Rambo toyline and cartoon which ended up coming out in 1986 and 1987. Issue #3 of the comic book featured the following retraction:
Despite Rocky not becoming a G.I. Joe action figure like Sgt. Slaughter, the Cobra nemesis they’d created to fight him did end up getting produced. So if you ever wondered why Cobra needed Big Boa, an evil boxing instructor? Well, now you know.